A. Field of the Invention
The present invention relates to a signal generator, more specifically, to a synchronizing signal generator for liquid crystal shutter glasses.
B. Description of the Related Art
For the human visual system, due to the independent visual system for the right eye and the left eye, the image captured by the right eye is different from the one captured by the left eye. Therefore, human can merge the individual images (parallax images) together and obtain a vision with depth perception. That is how the feeling of stereo comes from. Since general image systems do not output left image and right image, independently, viewers just can see plan image without the feeling of stereo. For providing stereo image, such as 3D movies, to viewers, a mechanism of stereoscope and field-sequential stereoscopic display is provided. The field-sequential stereoscopic display outputs a right image and a left image sequentially, and the left eye and the right eye of the stereoscope are shut synchronized with the right image and the left image. If the switching between left and right eyes is fast enough that human eyes can not distinguish the change of switching, then the feeling of stereo is generated. In addition, for generating ideal feeling of stereo, the switching between left and right eyes of the stereoscope should be synchronized with the left image and right image on the screen.
A shutter type of liquid crystal shutter glasses (hereinafter referred as shutter glasses) is useful for 3D stereo viewing. The shutter glasses does not shutter left eye or right eye by any mechanical shuttering, but shutter by alternately electrical signal. FIG. 1 illustrates a field-sequential stereo display with the shuttering states for a shutter glasses. The screen 100 displays in a way following the sequence as left image, right image, left image, . . . , meanwhile the right eye and left eye of the shutter glasses 110 are shut alternately and successively by a synchronizing signal. Therefore, viewers wearing the shutter glasses 110 can see the left image with left eye and see the right image with right eye to get the feeling of stereo.
FIG. 2 shows the timing chart for the shuttering signals of the shutter glasses. For image system, it generates a vertical synchronizing signal VSS for each image frame. A typical shutter glasses generates shuttering signals according to this vertical synchronizing signal. As being shown in FIG. 2, when a left eye image is displayed on the screen 100, the shuttering signal of right eye is at high level, and the right eye of the shutter glasses is shuttered and opaque. At the same time, the shuttering signal of left eye is at low level, and the left eye of the shutter glasses is transparent so that viewer can see the left image. Then, when a right eye image is displayed on the screen 100, the shuttering signal of right eye is at low level, and the right eye of the shutter glasses is transparent so that viewer can see the right image. At the same time, the shuttering signal of left eye is at high level, and the left eye of the shutter glasses is shuttered and opaque. Consequently, by alternately applying shuttering signals to the shutter glasses and displaying individual eye image on the screen 100, the stereo movies can be generated.
However, due to that shuttering signals of prior art is triggered by the vertical synchronization signal only, it is hard to tell whether the current displaying image belongs to left eye or right eye. Therefore, the shuttering signals can not be transmitted properly and in consequence, so that the left eye image and right eye image will be out of sequence. To solve the above problem, the user has to switch the stereo orientation of shutter glasses manually in order to display images synchronously.
Furthermore, due to the effect of different switching speed of the shutter glasses and the different phosphor decay rate of the monitor, the images displayed on the screen and their corresponding switching action of shutter glasses are out of step. It will thus result in eye and brain-strain of the viewer and fail to generate the 3D stereo view. For example, if the switching action is too early, the residual image to the previous eye view is visible to the other eye view; on the other hand, if the switching action is too late, user will see the top portion image on the wrong eye.
Whereas the above problem has occurred, the main purpose of the present invention is to provide a stereo synchronizing signal generator for shutter glasses, which can properly generate the stereo synchronizing signals.
Another purpose of the present invention is to provide a stereo synchronizing signal generator for shutter glasses, which allows the users to retard or lead the switching timing of the stereo synchronizing signal.
A further purpose of the present invention is to provide a stereo synchronizing signal generator for shutter glasses with different types of interface.
The stereo synchronizing signal generator for shutter glasses according to the present invention includes a signal generating unit for generating the preliminary shuttering signals PSS according to the vertical synchronizing signal and a start signal. A signal delaying unit is provided for delaying the preliminary shuttering signals PSS according to a value in a register. Then an output unit connected to the signal delaying unit for outputting the delayed signals into the shutter glasses.